Herein, greenhouse experiments were designed to reveal
the role
of nitrogen-doped carbon dots (N-CDs) in enhancing maize drought tolerance.
Two humidity conditions were created: adequate watering (soil moisture,
75%) and drought stress (soil moisture, 35%). Corn seedlings were
harvested after spraying the N-CD solution (5 mg·L–1) on maize leaves for 5 days. The results indicated that foliar application
of N-CDs increased the net photosynthesis rate (28.6%) of maize, and
the fresh and dry weights of roots and shoots increased by 224.5,
360.0, 230.8, and 63.3% under drought stress, respectively. N-CDs
showed high reactive oxygen species (ROS)-scavenging activity, resulting
in enhanced superoxide dismutase activity (26.7%) and reduced malondialdehyde
enzyme activity (18.9%). Besides, N-CDs could be used as light-harvesting
materials to improve the light utilization efficiency, upregulate psbA gene expression (81.7-fold), and promote fast synthesis
of the D1 protein, which could repair photosystem II under drought
stress. Therefore, foliar-sprayed N-CDs could improve photosynthesis
through multiple pathways under drought stress: light harvesting,
photoprotection, and light repairing. Then, N-CD exposure reduced
the corn yield loss under drought by nearly 30% compared with those
of the control groups in a full life cycle study. Therefore, this
study found for the first time that N-CD-enabled nanoagriculture could
ensure crop growth and yield under drought stress, which would be
important for global crop cultivation and a promising alternative
to deal with the global climate change.